WO2009115909A1

WO2009115909A1 - Method and apparatus for revoking resource allocations

Info

Publication number: WO2009115909A1
Application number: PCT/IB2009/000560
Authority: WO
Inventors: Frank Frederiksen; Kimmo Tapio Kettunen; Esa Mikael Malkamaki; Lars Erik Lindh
Original assignee: Nokia Corporation
Priority date: 2008-03-20
Filing date: 2009-03-19
Publication date: 2009-09-24

Abstract

An approach is provided for revoking allocated network (e.g., radio) resources. After a network allocates resources to a user equipment, the network revokes the allocation by generating a revoke command and transmitting the command to a user equipment. The network then determines acknowledgement of the revoke command by the user equipment.

Description

METHOD AND APPARATUS FOR REVOKING RESOURCE ALLOCATIONS

FIELD OF THE INVENTION

The present invention relates to a method and apparatus for revoking resource allocations (e.g., radio resource allocations) in a wireless telecommunications network.

BACKGROUND

Radio communication systems, such as a wireless data networks (e.g., Third Generation Partnership Project (3GPP) Long Term Evolution (LTE) systems, spread spectrum systems (such as Code Division Multiple Access (CDMA) networks), Time Division Multiple Access (TDMA) networks, Orthogonal Frequency Division Multiplexed (OFDMA) networks, spatially multiplexed networks, WiMAX (Worldwide Interoperability for Microwave Access), etc.), provide users with the convenience of mobility along with a rich set of services and features. This convenience has spawned significant adoption by an ever growing number of consumers as an accepted mode of communication for business and personal uses. To promote greater adoption, the telecommunication industry, from manufacturers to service providers, has agreed at great expense and effort to develop standards for communication protocols that underlie the various services and features. To support the concurrently scheduling of a large number of users for small and constant bit rate services, the concept of persistent or semi-persistent scheduling is introduced. However, persistently scheduled resources can be wasteful if the allocated resources are not utilized. Conventional approaches have not been able to efficiently de-allocate or revoke resources once the resources have been granted to a user.

SOME EXEMPLARY EMBODIMENTS

Therefore, there is a need for an approach for providing efficient revocation of resources, which can co-exist with already developed standards and protocols. According to one embodiment, a computer-readable storage medium carrying one or more sequences of one or more instructions which, when executed by one or more processors, cause the one or more processors to allocate radio resources to a user equipment. The one or more processors are also caused to generate a revoke command to revoke the allocation. The one or more processors are further caused to initiate transmission of the revoke command to the user equipment. The one or more processors are further caused to determine acknowledgement of the revoke command.

According to another embodiment, an apparatus comprising a processor and a memory storing executable instructions that if executed cause the apparatus to allocate radio resources to a user equipment. The processor and the memory are also caused to generate a revoke command to revoke the allocation. The processor and the memory are further caused to initiate transmission of the revoke command to the user equipment. The one or more processors are further caused to determine acknowledgement of the revoke command.

According to another embodiment, a method comprises allocating radio resources to a user equipment. The method also comprises generating a revoke command to revoke the allocation based on the determination. The method further comprises initiating transmission of the revoke command to the user equipment. The method further comprises determining acknowledgement of the revoke command.

According to another embodiment, a computer-readable storage medium carrying one or more sequences of one or more instructions which, when executed by one or more processors, cause the one or more processors to receive a revoke command to revoke an allocation of radio resources. The one or more processors are also caused to generate an acknowledgement of the revoke command. The one or more processors are further caused to initiate transmission of the acknowledgement to a base station. According to another embodiment, an apparatus comprising a processor and a memory storing executable instructions that if executed cause the apparatus to receive a revoke command to revoke the allocation of radio resources. The processor and the memory are also caused to generate an acknowledgement of the revoke command. The one or more processors are further caused to initiate transmission of the acknowledgement to a base station. According to yet another embodiment, a method comprises receiving a revoke command to revoke the allocation of radio resources. The method also comprises generating an acknowledgement of the revoke command. The one or more processors are further caused to initiate transmission of the acknowledgement to the base station. Still other aspects, features, and advantages of the invention are readily apparent from the following detailed description, simply by illustrating a number of particular embodiments and implementations, including the best mode contemplated for carrying out the invention. The invention is also capable of other and different embodiments, and its several details can be modified in various obvious respects, all without departing from the spirit and scope of the invention. Accordingly, the drawings and description are to be regarded as illustrative in nature, and not as restrictive. BRIEF DESCRIPTION OF THE DRAWINGS

The embodiments of the invention are illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings:

FIG. 1 is a diagram of a communication system capable of providing resource allocation and revocation, according to various exemplary embodiments of the invention;

FIG. 2 is a flowchart of a process for revoking resource allocations, according to an exemplary embodiment;

FIGs. 3A-3C are diagrams of processes relating to revoking scheduled resources and determining confirmation of the revocation, according to various exemplary embodiments; FIG. 4 is a flowchart of a process for receiving a command to revoke a resource allocation, according to an exemplary embodiment;

FIGs. 5A-5D are diagrams of communication systems having exemplary long-term evolution (LTE) architectures, in which the system of FIG. 1 can operate, according to various exemplary embodiments of the invention; FIG. 6 is a diagram of hardware that can be used to implement an embodiment of the invention;

FIG. 7 is a diagram of a chip set that can be used to implement an embodiment of the invention; and

FIG. 8 is a diagram of a mobile station (e.g., handset) that can be used to implement an embodiment of the invention.

DESCRIPTION OF PREFERRED EMBODIMENT

A method and apparatus for revoking resource allocations (e.g., radio resource allocations) are disclosed, hi the following description, for the purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the embodiments of the invention. It is apparent, however, to one skilled in the art that the embodiments of the invention may be practiced without these specific details or with an equivalent arrangement. In other instances, well-known structures and devices are shown in block diagram form in order to avoid unnecessarily obscuring the embodiments of the invention.

Although the embodiments of the invention are discussed with respect to a wireless network compliant with a 3GPP LTE or EUTRAN (Evolved Universal Terrestrial Radio Access Network)) architecture, it is recognized by one of ordinary skill in the art that the embodiments of the inventions have applicability to any type of packet based communication system and equivalent functional capabilities. Additionally, while the scheduling approach is explained in the context of the uplink, it is contemplated that the scheduling approach has applicability to the downlink as well.

FIG. 1 is a diagram of a communication system capable of providing resource allocation and revocation, according to various exemplary embodiments of the invention. As shown in FIG. 1, a communication system 100 (e.g., a wireless network) includes one or more user equipment (UEs) 101 that communicate with a base station 103, which is part of an access network (e.g., 3GPP LTE or E-UTRAN, etc.) (not shown). The UE 101 and base station 103 permit the allocation and subsequent revocation of network (e.g., radio) resources if the resources, for instance, are not needed by the UE 101.

By way of example, under the 3GPP LTE architecture (as shown in FIGs. 5A-5D), the base station 103 is denoted as an enhanced Node B (eNB). The UE 101 can be any type of mobile stations, such as handsets, terminals, stations, units, devices, multimedia tablets, Internet nodes, communicators, Personal Digital Assistants or any type of interface to the user (such as "wearable" circuitry, etc.). The UE 101 may be a fixed terminal, a mobile terminal, or a portable terminal. The system 100, according to one embodiment, operates using the Frequency Division Duplex (FDD) mode of 3GPP, as well as a Time Domain Duplexing (TDD) mode.

In exemplary embodiments, the UE 101 includes a transceiver and an antenna system (not shown) that couples to the transceiver to receive or transmit signals from the eNB 103; the antenna system can include one or more antennas. Similarly, the eNB 103 employs a transceiver (not shown) to exchange information with the UE 101 via one or more antennas, which transmit and receive electromagnetic signals. For instance, the eNB 103 may utilize a Multiple Input Multiple Output (MIMO) antenna system for supporting the parallel transmission of independent data streams to achieve high data rates with the UE 101. The eNB 103 may use orthogonal frequency divisional multiplexing (OFDM) as a downlink (DL) transmission scheme and a single-carrier transmission (e.g., single carrier-frequency division multiple access (SC-FDMA)) with cyclic prefix for the uplink (UL) transmission scheme. SC-FDMA can also be realized using a DFT-S-OFDM principle, which is detailed in 3GGP TR 25.814, entitle "Physical Layer Aspects for Evolved UTRA," v.1.5.0, May 2006 (which is incorporated herein by reference in its entirety). SC-FDMA, also referred to as Multi-User-SC-FDMA, allows multiple users to transmit simultaneously on different sub-bands.

By way of example, in LTE, the eNB 103 controls allocation of the network (e.g., radio) resources using the resource allocation logic 105; that is, all control of the network resources are granted and revoked by the eNB 103. As mentioned, the revocation of resource allocations poses a challenge, particularly when the resource allocations are persistent or semi-persistent. Under a persistent or semi-persistent allocation scheme, the system 100 assigns resources (e.g., relating to a communication link of the access network) to the UE 101, which then operates the assigned resources (e.g., channel) without explicit usage of the associated control channels. By way of example, the system of 100 is described with respect to uplink persistent resource allocations within a 3GPP LTE architecture.

Typically, the UE 101 and eNB 103 regularly exchange control information. Such control information, in an exemplary embodiment, is transported over a control channel on, for example, the downlink from the eNB 103 to the UE 101. By way of example, a number of communication channels are defined for use in the system 100. The channel types include: physical channels, transport channels, and logical channels. For instance in LTE system, the physical channels include, among others, a Physical Downlink Shared channel (PDSCH), Physical Downlink Control Channel (PDCCH), Physical Uplink Shared Channel (PUSCH), and Physical Uplink Control Channel (PUCCH). The transport channels can be defined by how they transfer data over the radio interface and the characteristics of the data. In LTE downlink, the transport channels include, among others, a broadcast channel (BCH), paging channel (PCH), and Down Link Shared Channel (DL-SCH). In LTE uplink, the exemplary transport channels are a Random Access Channel (RACH) and UpLink Shared Channel (UL-SCH). Each transport channel is mapped to one or more physical channels according to its physical characteristics.

Each logical channel can be defined by the type and required Quality of Service (QoS) of information that it carries. In LTE system, the associated logical channels include, for example, a broadcast control channel (BCCH), a paging control channel (PCCH), Dedicated

Control Channel (DCCH), Common Control Channel (CCCH), Dedicated Traffic Channel

(DTCH), etc.

In LTE system, the BCCH (Broadcast Control Channel) can be mapped onto both BCH and DL-SCH. As such, this is mapped to the PDSCH; the time-frequency resource can be dynamically allocated by using L1/L2 control channel (PDCCH). In this case, BCCH (Broadcast

Control Channel)-RNTI (Radio Network Temporary Identifier) is used to identify the resource allocation information.

Under the LTE architecture, fast hybrid automatic repeat request (H-ARQ) can be used to increase spectral efficiency. The normal H-ARQ operation for dynamic scheduled uplink data is that for each uplink resource grant (signaled on a downlink control channel (e.g., Physical Downlink Control Channel (PDCCH)) there is an associated H-ARQ feedback channel for positive and negative acknowledgements (ACK/NACK). It is recognized that there is a delay between the time of the uplink grant (on the PDCCH) to the time when the UE actually transmits uplink data, and further to the time when the eNB should send the ACK/NACK on the PHICH (Physical H-ARQ indication channel). According to one embodiment, the order of the UL grant presents a mapping for the UE so that the UE will know where on the PHICH the associated ACK/NACK report will be sent. Both the eNB and UE are configured to execute this H-ARQ scheme via error control logic (not shown).

Under one assumption, the scheduling delay can be, for instance, 3 ms (plus the delay of the actual signaling on the PDCCH), and that the eNode B processing time is also 3 ms. As such, the timing relation for a single H-ARQ process or channel can be shown in Table 1 :

Table 1

In one embodiment, it is further assumed that the UL H-ARQ retransmission operation is synchronous. That is, the H-ARQ retransmission delay is fixed. In case that non-adaptive H- ARQ is used for the uplink (i.e., uplink retransmissions are performed on the same physical resources), the eNB 103 provides an indication of whether retransmission is to be performed over the uplink. In an exemplary embodiment, this can be handled through PHICH signaling, whereby a UE is assigned a PHICH resource through the physical resources that is being granted for uplink transmission. One mapping for this could be to map the first PRB index of the uplink grant to an associated PHICH.

It is noted that persistently (or semi-persistently) allocated resources can be configured using higher layer signaling, while the actual assignment of resources utilize dedicated Ll control signaling. With persistent uplink allocations, it is recognized that some issues exist with respect to revoking the resources. These issues are illustrated in the following example procedure for allocating and revoking persistent resource allocations:

An UE is configured to be ready to enter a "persistent mode" of operation; i.e., periodicity and other parameters are configured using higher layer signaling (Radio Resource Control (RRC)). For instance, the periodicity for an uplink is configured for a predetermined period (e.g., 20 ms). The PDCCH is used for the resource grant. Consequently, the L1/L2 control channel is used to provide a number of physical uplink resources that the UE 101 is allowed to use for uplink transmissions. More specifically, the resources are granted to the UE 101 according to the configured periodicity, e.g., for the 20 ms periodicity, the physical resources are granted for uplink transmission resources every 20 ms).

When the uplink resources are not needed by the UE, the resources are revoked, and the UE returns to the "being ready" state again.

Under a traditional system, the above procedure encounters the potential problem associated with the fact that there is no guarantee that the revoke command is received and decoded correctly by the UE 101. If the revoke command is not properly received, the UE 101 subsequently continues transmitting on the allocated resources (which now are being granted to other users by the eNB 103). As a consequence, there can be a high risk of collisions of transmitted data packets, and thereby a loss of information. Conventional approaches have not addressed the above described problem. One conventional approach utilizes an implicit resource revocation based on empty buffer status report sent by the UE 101. Under this implicit release approach, the UEs 101 autonomously release their resources by sending an empty buffer status report to the eNB 103. For instance, the resource allocation logic 107 of the UE 101 determines the status of a buffer 109 to generate the buffer status report. However, this approach loses some efficiency because the UE 101 may have lower priority data in the buffer and will thus not report an empty buffer. In such a case, the eNB 103 may explicitly send a resource revocation command, but would still face the problem of not being able to determine acknowledgement that the UE 101 has properly decoded the revocation command. Another approach relies on the use of a discontinuous transmission (DTX) detection mechanism. For example, under this approach, the eNB 103 may be configured to include a DTX detection logic 111 to detect gaps in the data transmissions from a UE 101. During gaps, for instance, the DTX detection logic 111 informs the eNB 103 that the corresponding resource is not needed and can be revoked. However, the problem of a lack of an explicit acknowledgement of the revocation from the UE 101 remains.

To address this problem and reduce the risk of collisions of transmitted data packets, the system 100 provides for signaling of an acknowledgement by the UE 101 that the UE 101 has successfully received a resource revocation command from the eNB 103.

FIG. 2 is a flowchart of process for revoking resource allocations, according to an exemplary embodiment. In one embodiment, the process 200 is implemented in, for instance, a chip set including a processor and a memory as shown FIG. 7. In step 201, the eNB 103 allocates resources (e.g., persistent or semi-persistent resources) relating to, for instance, a communication link of a network (e.g., physical resource blocks (PRBs) for an uplink). After the resource grant, the eNB 103 makes, for example, periodic determinations of whether the allocated resources are needed by the UE 101 (step 203). By way of example, the eNB 103 determines whether a resource is needed by a UE 101 by monitoring buffer status reports from the UE 101. An empty buffer 101, for instance, indicates that the UE 101 does not need the allocated resources. It is also contemplated that the eNB 103 may use any other method or mechanism to make this determination. If the eNB 103 determines that the allocated resources are needed by the UE 101, the eNB 103 continues to receive transmission from the UE 101 over the allocated resources (e.g., over the uplink) (step 205). If the eNB 103 detects that the allocated resources are not need by the UE 101, the eNB 103 generates a revoke command to revoke the allocation of the resources to the UE 101 (step 207). It is noted that in certain embodiments, the eNB 103 need not make a determination of whether the UE 101 needs the allocated resource before revoking the allocated resources (i.e., the eNB 103 may revoke the allocated resources without performing the determination of step 203). The eNB 103 then initiates transmission of the revoke command to the UE 101 (step 209) and receives an acknowledgement from the UE 101 confirming successful receipt and decoding of the revoke command (step 211). By way of example, the eNB 103 transmits the revoke command on a PDCCH, and the UE 101 transmits the corresponding acknowledgement using a PUCCH resource derived from the PDCCH resource on which the revoke command was received. In certain embodiments, the UE 101 may also signal the acknowledgement using the revoked resource allocation (e.g., the revoked uplink or downlink resource). Alternatively or additionally, the eNB 103 may implicitly determine acknowledgement of the revoke command by using a DTX detection mechanism (e.g., DTX detection logic 111) to determine whether the UE 101 has stopped using the revoked resources. For instance, the DTX detection logic 111 may detect that the UE 101 has stopped transmitting on the allocated resources following transmission of a command to revoke the resource allocation. In such a case, the DTX detection acts as the acknowledgement that the UE 101 has successfully received and decoded the revoke command. Consequently, the UE 101 need not explicitly signal acknowledgement of the revoke command.

The process of FIG. 2 is further elaborated below in FIGs. 3A-3C, according to the various embodiments. FIGs. 3A-3C are diagrams of processes relating to revoking scheduled resources and determining confirmation of the revocation, according to various exemplary embodiments. FIGs. 3A-3C are time sequence diagrams illustrating the process of revoking allocated resources. FIG. 3A illustrates the process for resource revocation/acknowledgement using the existing 3GPP framework, FIG. 3B illustrates the process for resource revocation/acknowledgement including a pseudo noise sequence to identify the UE 101, and FIG. 3C illustrates the process for resource revocation/acknowledgement using implicit confirmation via DTX detection.

In these diagrams, a network process is illustrated by a thin vertical line. A message passed from one process to another is represented by horizontal arrows. A step performed by a process is indicated by a box overlapping the process at a time sequence indicated by the vertical position of the box or arrow. The processes represented in FIGs. 3A-3C are a UE 101 and an eNB 103.

In exemplary embodiments, a revoke command is signaled to the UE 101 for revoking persistently allocated uplink physical resources using an Ll protocol. Along with the revoke command, Ll acknowledgement of the revocation of some persistently uplink allocated resources can be utilized. In other words, activation or deactivation of the control channel is to be acknowledged by the UE 101. Revoke acknowledgement signaling can be provided as follows: (1) employ a signaling system that uses the existing 3GPP framework, or (2) implement a revoke acknowledgement that takes the form of a physical signal which is transmitted on all or some of the persistently allocated uplink resources, such that the eNB 103 can verify that the UE 101 actually received the revoke message of the persistently allocated resources.

As shown in FIG. 3A, the eNB 103 grants a persistent or semi-persistent allocation of resources 301 to the UE 101. The eNB 103 generates and transmits a revoke command using, for instance, an "invalid" uplink resource grant (e.g., a zero transport block size, zero physical resource block (PRB) allocation, or an invalid combination of bits) using, for instance, on a downlink control channel (e.g., a PDCCH) (at 303). The UE 101 is configured to interpret the invalid resource grant such that the UE 101 knows that the persistent allocation has been revoked. At 305, the UE 101 decodes the revoke command and knows that the resource has been revoked. Instead of an invalid uplink grant, the revoke command may also be, for instance, a dedicated control message, e.g., a pre-defined value for a given parameter or a combination of parameters.

To acknowledge receipt of the revoke command, the UE 101 is configured to transmit an acknowledgement on, for example, the physical uplink control channel (PUCCH) (at 307). Normally, the PUCCH is used only for downlink allocations. However, because the uplink and downlink PDCCH share the same control channel element (CCE) resources, and also because the downlink PDCCH will not be transmitted on the same CCE, the CCE index of the uplink PDCCH for the revoke command can be used to reference a PUCCH resource. In this example, the PUCCH resource is not taken by or reserved for acknowledgement of the downlink traffic.

FIG. 3B illustrates a process for using an acknowledgement including a pseudo noise sequence to identify the UE 101. At 321, the eNB 103 grants a persistent or semi-persistent allocation of resources to the UE 101. The eNB 103 then determines that the UE 101 does not need the resource allocation and transmits a revoke command (e.g., a physical revoke confirmation signal using Ll or MAC) to the UE 101 (at 323). On successful receipt and decoding of the revoke command, the UE 101 generates an acknowledgement (at 325). It is contemplated that the acknowledgement can be configured to be specific to the UE 101 and can be used to identify the UE 101. For example, the acknowledgement can be a pseudo noise sequence based on the cell specific radio network temporary identifier (c-RNTI) associated with the UE 101 (e.g., a Gold sequence or other similar sequence with good correlation to the individual UE 101). The acknowledgement is then transmitted to the eNB 103 using, for instance, one or all allocated physical resource blocks (PRBs) (at 327).

It should be noted that the alternative to using an explicit acknowledgement of the revoke command is implementation of a DTX detection mechanism (FIG. 3C), which acts in place of the acknowledgement. As shown in FIG. 3C, the eNB 103 grants a persistent or semi-persistent allocation of resources to the UE 101 (at 341). As with the processes of FIGs. 3A and 3B, the eNB 103 then determines that the UE 101 does not need the resource allocation and transmits a revoke command (e.g., a physical revoke confirmation signal using Ll or MAC) to the UE 101 (at 343). On receipt of the revoke command, the UE 101 decodes the command and stops using the resources as directed (at 345), but does not explicitly send an acknowledgement to the eNB 103. Instead, the eNB 103 uses the DTX detection mechanism to determine, for instance, that the UE 101 has stopped transmitting using the allocated resources after the eNB 103 issued the revoke command (at 347).

FIG. 4 is a flowchart of a process for receiving a command to revoke a resource allocation, according to an exemplary embodiment. In one embodiment, the process 400 is implemented in, for instance, a chip set including a processor and a memory as shown FIG. 7. In step 401, the UE 101 receives a revoke command from the eNB 103 for revocation of previously allocated network resources. The UE 101 decodes the command and stops using the revoked resources as directed by the revoke command (step 403). The process of stopping the use of the revoked resources includes the UE 101 stopping any transmitting on the revoked resources. In certain embodiments, the UE 101 is configured to generate an explicit acknowledgment signal using the processes as described with respect to FIGs. 2 and 3A-3C (step 405). The acknowledgement is then transmitted to the eNB 103 using, for example, an Ll protocol, MAC protocol, or the PUCCH (step 407).

In other embodiments, the UE 101 need not transmit an explicit acknowledgement. Instead, the eNB 103 detects receipt of the revoke command by the UE 101 using a DTX detection mechanism. For instance, detecting the discontinuation of transmissions on the revoked resources is an implicit acknowledgement of receipt of the revoke command.

FIGs. 5A-5D are diagrams of communication systems having exemplary LTE architectures, in which the system 100 of FIG. 1 can operate, according to various exemplary embodiments of the invention. By way of example (as discussed with respect to FIG. 2), the base stations 103 and the UEs 101 can communicate in system 500 using any access scheme, such as Time Division Multiple Access (TDMA), Code Division Multiple Access (CDMA), Wideband Code Division Multiple Access (WCDMA), Orthogonal Frequency Division Multiple Access (OFDMA) or Single Carrier Frequency Division Multiple Access (SC-FDMA) or a combination thereof. In an exemplary embodiment, both uplink and downlink can utilize WCDMA. In another exemplary embodiment, uplink utilizes SC-FDMA, while downlink utilizes OFDMA.

The communication system 500 is compliant with 3GPP LTE, entitled "Long Term Evolution of the 3GPP Radio Technology" (which is incorporated herein by reference in its entirety). As shown in FIG. 5A, one or more user equipment (UEs) 101 communicate with a network equipment, such as a base station 103, which is part of an access network (e.g., WiMAX (Worldwide Interoperability for Microwave Access), 3GPP LTE (or E-UTRAN), etc.). Under the 3GPP LTE architecture, base station 103 is denoted as an enhanced Node B (eNB).

The MME (Mobile Management Entity )/Serving Gateways 501 are connected to the eNBs 103 in a full or partial mesh configuration using tunneling over a packet transport network (e.g., Internet Protocol (IP) network) 503. Exemplary functions of the MME/Serving GW 501 include distribution of paging messages to the eNBs 103, IP header compression, termination of U-plane packets for paging reasons, and switching of U-plane for support of UE mobility. Since the GWs 501 serve as a gateway to external networks, e.g., the Internet or private networks 503, the GWs 501 include an Access, Authorization and Accounting system (AAA) 505 to securely determine the identity and privileges of a user and to track each user's activities. Namely, the MME Serving Gateway 501 is the key control-node for the LTE access-network and is responsible for idle mode UE tracking and paging procedure including retransmissions. Also, the MME 501 is involved in the bearer activation/deactivation process and is responsible for selecting the SGW (Serving Gateway) for a UE at the initial attach and at time of intra-LTE handover involving Core Network (CN) node relocation. A more detailed description of the LTE interface is provided in 3GPP TR 25.813, entitled "E-UTRA and E-UTRAN: Radio Interface Protocol Aspects," which is incorporated herein by reference in its entirety.

In FIG. 5B, a communication system 502 supports GERAN (GSM/EDGE radio access) 504, and UTRAN 506 based access networks, E-UTRAN 512 and non-3GPP (not shown) based access networks, and is more fully described in TR 23.882, which is incorporated herein by reference in its entirety. A key feature of this system is the separation of the network entity that performs control-plane functionality (MME 508) from the network entity that performs bearer- plane functionality (Serving Gateway 510) with a well defined open interface between them SI l. Since E-UTRAN 512 provides higher bandwidths to enable new services as well as to improve existing ones, separation of MME 508 from Serving Gateway 510 implies that Serving Gateway 510 can be based on a platform optimized for signaling transactions. This scheme enables selection of more cost-effective platforms for, as well as independent scaling of, each of these two elements. Service providers can also select optimized topological locations of Serving Gateways 510 within the network independent of the locations of MMEs 508 in order to reduce optimized bandwidth latencies and avoid concentrated points of failure.

As seen in FIG. 5B, the E-UTRAN (e.g., eNB) 512 interfaces with UE via LTE-Uu. The E-UTRAN 512 supports LTE air interface and includes functions for radio resource control (RRC) functionality corresponding to the control plane MME 508. The E-UTRAN 512 also performs a variety of functions including radio resource management, admission control, scheduling, enforcement of negotiated uplink (UL) QoS (Quality of Service), cell information broadcast, ciphering/deciphering of user, compression/decompression of downlink and uplink user plane packet headers and Packet Data Convergence Protocol (PDCP).

The MME 508, as a key control node, is responsible for managing mobility UE identifies and security parameters and paging procedure including retransmissions. The MME 508 is involved in the bearer activation/deactivation process and is also responsible for choosing

Serving Gateway 510 for the UE 101. MME 508 functions include Non Access Stratum (NAS) signaling and related security. MME 508 checks the authorization of the UE 101 to camp on the service provider's Public Land Mobile Network (PLMN) and enforces UE 101 roaming restrictions. The MME 508 also provides the control plane function for mobility between LTE and 2G/3G access networks with the S3 interface terminating at the MME 508 from the SGSN

(Serving GPRS Support Node) 514.

The SGSN 514 is responsible for the delivery of data packets from and to the mobile stations within its geographical service area. Its tasks include packet routing and transfer, mobility management, logical link management, and authentication and charging functions. The S6a interface enables transfer of subscription and authentication data for authenticating/authorizing user access to the evolved system (AAA interface) between MME 508 and HSS (Home Subscriber Server) 516. The SlO interface between MMEs 508 provides MME relocation and MME 508 to MME 508 information transfer. The Serving Gateway 510 is the node that terminates the interface towards the E-UTRAN 512 via Sl-U.

The Sl-U interface provides a per bearer user plane tunneling between the E-UTRAN 512 and Serving Gateway 510. It contains support for path switching during handover between eNBs 512. The S4 interface provides the user plane with related control and mobility support between SGSN 514 and the 3GPP Anchor function of Serving Gateway 510.

The S 12 is an interface between UTRAN 406 and Serving Gateway 510. Packet Data Network (PDN) Gateway 518 provides connectivity to the UE to external packet data networks by being the point of exit and entry of traffic for the UE. The PDN Gateway 518 performs policy enforcement, packet filtering for each user, charging support, lawful interception and packet screening. Another role of the PDN Gateway 518 is to act as the anchor for mobility between 3GPP and non-3GPP technologies such as WiMAX and 3GPP2 (CDMA IX and EvDO (Evolution Data Only)).

The S7 interface provides transfer of QoS policy and charging rules from PCRF (Policy and Charging Role Function) 520 to Policy and Charging Enforcement Function (PCEF) in the PDN Gateway 518. The SGi interface is the interface between the PDN Gateway and the operator's IP services including packet data network 522. Packet data network 522 may be an operator external public or private packet data network or an intra operator packet data network, e.g., for provision of DVIS (EP Multimedia Subsystem) services. Rx+ is the interface between the PCRF and the packet data network 522. As seen in FIG. 5C, the eNB utilizes an E-UTRA (Evolved Universal Terrestrial Radio

Access) (user plane, e.g., RLC (Radio Link Control) 515, MAC (Media Access Control) 517, and PHY (Physical) 519, as well as a control plane (e.g., RRC 521)). The eNB also includes the following functions: Inter Cell RRM (Radio Resource Management) 523, Connection Mobility Control 525, RB (Radio Bearer) Control 527, Radio Admission Control 529, eNB Measurement Configuration and Provision 531, and Dynamic Resource Allocation (Scheduler) 533.

The eNB communicates with the aGW 501 (Access Gateway) via an Sl interface. The aGW 501 includes a User Plane 501a and a Control plane 501b. The control plane 501b provides the following components: SAE (System Architecture Evolution) Bearer Control 535 and MM (Mobile Management) Entity 537. The user plane 501b includes a PDCP (Packet Data Convergence Protocol) 539 and a user plane functions 541. It is noted that the functionality of the aGW 501 can also be provided by a combination of a serving gateway (SGW) and a packet data network (PDN) GW. The aGW 501 can also interface with a packet network, such as the Internet 543. In an alternative embodiment, as shown in FIG. 5D, the PDCP (Packet Data Convergence

Protocol) functionality can reside in the eNB rather than the GW 501. Other than this PDCP capability, the eNB functions of FIG. 5C are also provided in this architecture.

In the system of HG. 5D, a functional split between E-UTRAN and EPC (Evolved Packet Core) is provided. In this example, radio protocol architecture of E-UTRAN is provided for the user plane and the control plane. A more detailed description of the architecture is provided in 3GPP TS 36.300.

The eNB 103 interfaces via the Sl to the Serving Gateway 545, which includes a Mobility Anchoring function 547. According to this architecture, the MME (Mobility Management Entity) 549 provides SAE (System Architecture Evolution) Bearer Control 551, Idle State Mobility Handling 553, and NAS (Non-Access Stratum) Security 555.

One of ordinary skill in the art would recognize that the processes for allocation and revoking resources may be implemented via software, hardware (e.g., general processor, Digital

Signal Processing (DSP) chip, an Application Specific Integrated Circuit (ASIC), Field

Programmable Gate Arrays (FPGAs), etc.), firmware, or a combination thereof. Such exemplary hardware for performing the described functions is detailed below with respect to FIG. 6.

FIG. 6 illustrates a computer system 600 upon which an embodiment of the invention may be implemented. Computer system 600 is programmed to carry out the inventive functions described herein and includes a communication mechanism such as a bus 610 for passing information between other internal and external components of the computer system 600. Information (also called data) is represented as a physical expression of a measurable phenomenon, typically electric voltages, but including, in other embodiments, such phenomena as magnetic, electromagnetic, pressure, chemical, biological, molecular, atomic, sub-atomic and quantum interactions. For example, north and south magnetic fields, or a zero and non-zero electric voltage, represent two states (0, 1) of a binary digit (bit). Other phenomena can represent digits of a higher base. A superposition of multiple simultaneous quantum states before measurement represents a quantum bit (qubit). A sequence of one or more digits constitutes digital data that is used to represent a number or code for a character. In some embodiments, information called analog data is represented by a near continuum of measurable values within a particular range. A bus 610 includes one or more parallel conductors of information so that information is transferred quickly among devices coupled to the bus 610. One or more processors 602 for processing information are coupled with the bus 610.

A processor 602 performs a set of operations on information. The set of operations include bringing information in from the bus 610 and placing information on the bus 610. The set of operations also typically include comparing two or more units of information, shifting positions of units of information, and combining two or more units of information, such as by addition or multiplication or logical operations like OR, exclusive OR (XOR), and AND. Each operation of the set of operations that can be performed by the processor is represented to the processor by information called instructions, such as an operation code of one or more digits. A sequence of operations to be executed by the processor 602, such as a sequence of operation codes, constitute processor instructions, also called computer system instructions or, simply, computer instructions. Processors may be implemented as mechanical, electrical, magnetic, optical, chemical or quantum components, among others, alone or in combination. Computer system 600 also includes a memory 604 coupled to bus 610. The memory 604, such as a random access memory (RAM) or other dynamic storage device, stores information including processor instructions. Dynamic memory allows information stored therein to be changed by the computer system 600. RAM allows a unit of information stored at a location called a memory address to be stored and retrieved independently of information at neighboring addresses. The memory 604 is also used by the processor 602 to store temporary values during execution of processor instructions. The computer system 600 also includes a read only memory (ROM) 606 or other static storage device coupled to the bus 610 for storing static information, including instructions, that is not changed by the computer system 600. Some memory is composed of volatile storage that loses the information stored thereon when power is lost. Also coupled to bus 610 is a non-volatile (persistent) storage device 608, such as a magnetic disk, optical disk or flash card, for storing information, including instructions, that persists even when the computer system 600 is turned off or otherwise loses power.

Information, including instructions, is provided to the bus 610 for use by the processor from an external input device 612, such as a keyboard containing alphanumeric keys operated by a human user, or a sensor. A sensor detects conditions in its vicinity and transforms those detections into physical expression compatible with the measurable phenomenon used to represent information in computer system 600. Other external devices coupled to bus 610, used primarily for interacting with humans, include a display device 614, such as a cathode ray tube (CRT) or a liquid crystal display (LCD), or plasma screen or printer for presenting text or images, and a pointing device 616, such as a mouse or a trackball or cursor direction keys, or motion sensor, for controlling a position of a small cursor image presented on the display 614 and issuing commands associated with graphical elements presented on the display 614. In some embodiments, for example, in embodiments in which the computer system 600 performs all functions automatically without human input, one or more of external input device 612, display device 614 and pointing device 616 is omitted.

In the illustrated embodiment, special purpose hardware, such as an application specific integrated circuit (ASIC) 620, is coupled to bus 610. The special purpose hardware is configured to perform operations not performed by processor 602 quickly enough for special purposes. Examples of application specific ICs include graphics accelerator cards for generating images for display 614, cryptographic boards for encrypting and decrypting messages sent over a network, speech recognition, and interfaces to special external devices, such as robotic arms and medical scanning equipment that repeatedly perform some complex sequence of operations that are more efficiently implemented in hardware.

Computer system 600 also includes one or more instances of a communications interface 670 coupled to bus 610. Communication interface 670 provides a one-way or two-way communication coupling to a variety of external devices that operate with their own processors, such as printers, scanners and external disks. In general the coupling is with a network link 678 that is connected to a local network 680 to which a variety of external devices with their own processors are connected. For example, communication interface 670 may be a parallel port or a serial port or a universal serial bus (USB) port on a personal computer. In some embodiments, communications interface 670 is an integrated services digital network (ISDN) card or a digital subscriber line (DSL) card or a telephone modem that provides an information communication connection to a corresponding type of telephone line. In some embodiments, a communication interface 670 is a cable modem that converts signals on bus 610 into signals for a communication connection over a coaxial cable or into optical signals for a communication connection over a fiber optic cable. As another example, communications interface 670 may be a local area network (LAN) card to provide a data communication connection to a compatible LAN, such as Ethernet. Wireless links may also be implemented. For wireless links, the communications interface 670 sends or receives or both sends and receives electrical, acoustic or electromagnetic signals, including infrared and optical signals, that carry information streams, such as digital data. For example, in wireless handheld devices, such as mobile telephones like cell phones, the communications interface 670 includes a radio band electromagnetic transmitter and receiver called a radio transceiver.

The term computer-readable medium is used herein to refer to any medium that participates in providing information to processor 602, including instructions for execution. Such a medium may take many forms, including, but not limited to, non-volatile media, volatile media and transmission media. Non-volatile media include, for example, optical or magnetic disks, such as storage device 608. Volatile media include, for example, dynamic memory 604. Transmission media include, for example, coaxial cables, copper wire, fiber optic cables, and carrier waves that travel through space without wires or cables, such as acoustic waves and electromagnetic waves, including radio, optical and infrared waves. Signals include man-made transient variations in amplitude, frequency, phase, polarization or other physical properties transmitted through the transmission media. Common forms of computer-readable media include, for example, a floppy disk, a flexible disk, hard disk, magnetic tape, any other magnetic medium, a CD-ROM, CDRW, DVD, any other optical medium, punch cards, paper tape, optical mark sheets, any other physical medium with patterns of holes or other optically recognizable indicia, a RAM, a PROM, an EPROM, a FLASH-EPROM, any other memory chip or cartridge, a carrier wave, or any other medium from which a computer can read.

FIG. 7 illustrates a chip set 700 upon which an embodiment of the invention may be implemented. Chip set 700 is programmed to carry out the inventive functions described herein and includes, for instance, the processor and memory components described with respect to FIG.

6 incorporated in one or more physical packages. By way of example, a physical package includes an arrangement of one or more materials, components, and/or wires on a structural assembly (e.g., a baseboard) to provide one or more characteristics such as physical strength, conservation of size, and/or limitation of electrical interaction.

In one embodiment, the chip set 700 includes a communication mechanism such as a bus 701 for passing information among the components of the chip set 700. A processor 703 has connectivity to the bus 701 to execute instructions and process information stored in, for example, a memory 705. The processor 703 may include one or more processing cores with each core configured to perform independently. A multi-core processor enables multiprocessing within a single physical package. Examples of a multi-core processor include two, four, eight, or greater numbers of processing cores. Alternatively or in addition, the processor 703 may include one or more microprocessors configured in tandem via the bus 701 to enable independent execution of instructions, pipelining, and multithreading. The processor 703 may also be accompanied with one or more specialized components to perform certain processing functions and tasks such as one or more digital signal processors (DSP) 707, or one or more application- specific integrated circuits (ASIC) 709. A DSP 707 typically is configured to process real-world signals (e.g., sound) in real time independently of the processor 703. Similarly, an ASIC 709 can be configured to performed specialized functions not easily performed by a general purposed processor. Other specialized components to aid in performing the inventive functions described herein include one or more field programmable gate arrays (FPGA) (not shown), one or more controllers (not shown), or one or more other special-purpose computer chips.

The processor 703 and accompanying components have connectivity to the memory 705 via the bus 701. The memory 705 includes both dynamic memory (e.g., RAM, magnetic disk, writable optical disk, etc.) and static memory (e.g., ROM, CD-ROM, etc.) for storing executable instructions that when executed perform the inventive steps described herein. The memory 705 also stores the data associated with or generated by the execution of the inventive steps.

FIG. 8 is a diagram of exemplary components of a mobile station (e.g., handset) capable of operating in the system of FIG. 1, according to an exemplary embodiment. Generally, a radio receiver is often defined in terms of front-end and back-end characteristics. The front-end of the receiver encompasses all of the Radio Frequency (RF) circuitry whereas the back-end encompasses all of the base-band processing circuitry. Pertinent internal components of the telephone include a Main Control Unit (MCU) 803, a Digital Signal Processor (DSP) 805, and a receiver/transmitter unit including a microphone gain control unit and a speaker gain control unit. A main display unit 807 provides a display to the user in support of various applications and mobile station functions. An audio function circuitry 809 includes a microphone 811 and microphone amplifier that amplifies the speech signal output from the microphone 811. The amplified speech signal output from the microphone 811 is fed to a coder/decoder (CODEC) 813.

A radio section 815 amplifies power and converts frequency in order to communicate with a base station, which is included in a mobile communication system, via antenna 817. The power amplifier (PA) 819 and the transmitter/modulation circuitry are operationally responsive to the MCU 803, with an output from the PA 819 coupled to the duplexer 821 or circulator or antenna switch, as known in the art. The PA 819 also couples to a battery interface and power control unit 820. In use, a user of mobile station 801 speaks into the microphone 811 and his or her voice along with any detected background noise is converted into an analog voltage. The analog voltage is then converted into a digital signal through the Analog to Digital Converter (ADC) 823. The control unit 803 routes the digital signal into the DSP 805 for processing therein, such as speech encoding, channel encoding, encrypting, and interleaving. In the exemplary embodiment, the processed voice signals are encoded, by units not separately shown, using a cellular transmission protocol such as global evolution (EDGE), general packet radio service (GPRS), global system for mobile communications (GSM), Internet protocol multimedia subsystem (MS), universal mobile telecommunications system (UMTS), etc., as well as any other suitable wireless medium, e.g., microwave access (WiMAX), Long Term Evolution (LTE) networks, code division multiple access (CDMA), wireless fidelity (WiFi), satellite, and the like.

The encoded signals are then routed to an equalizer 825 for compensation of any frequency-dependent impairments that occur during transmission though the air such as phase and amplitude distortion. After equalizing the bit stream, the modulator 827 combines the signal with a RF signal generated in the RF interface 829. The modulator 827 generates a sine wave by way of frequency or phase modulation. In order to prepare the signal for transmission, an up- converter 831 combines the sine wave output from the modulator 827 with another sine wave generated by a synthesizer 833 to achieve the desired frequency of transmission. The signal is then sent through a PA 819 to increase the signal to an appropriate power level. In practical systems, the PA 819 acts as a variable gain amplifier whose gain is controlled by the DSP 805 from information received from a network base station. The signal is then filtered within the duplexer 821 and optionally sent to an antenna coupler 835 to match impedances to provide maximum power transfer. Finally, the signal is transmitted via antenna 817 to a local base station. An automatic gain control (AGC) can be supplied to control the gain of the final stages of the receiver. The signals may be forwarded from there to a remote telephone which may be another cellular telephone, other mobile phone or a land-line connected to a Public Switched Telephone Network (PSTN), or other telephony networks.

Voice signals transmitted to the mobile station 801 are received via antenna 817 and immediately amplified by a low noise amplifier (LNA) 837. A down-converter 839 lowers the carrier frequency while the demodulator 841 strips away the RF leaving only a digital bit stream.

The signal then goes through the equalizer 825 and is processed by the DSP 805. A Digital to

Analog Converter (DAC) 843 converts the signal and the resulting output is transmitted to the user through the speaker 845, all under control of a Main Control Unit (MCU) 803-which can be implemented as a Central Processing Unit (CPU) (not shown).

The MCU 803 receives various signals including input signals from the keyboard 847. The MCU 803 delivers a display command and a switch command to the display 807 and to the speech output switching controller, respectively. Further, the MCU 803 exchanges information with the DSP 805 and can access an optionally incorporated SIM card 849 and a memory 851. In addition, the MCU 803 executes various control functions required of the station. The DSP 805 may, depending upon the implementation, perform any of a variety of conventional digital processing functions on the voice signals. Additionally, DSP 805 determines the background noise level of the local environment from the signals detected by microphone 811 and sets the gain of microphone 81 1 to a level selected to compensate for the natural tendency of the user of the mobile station 801. The CODEC 813 includes the ADC 823 and DAC 843. The memory 851 stores various data including call incoming tone data and is capable of storing other data including music data received via, e.g., the global Internet. The software module could reside in RAM memory, flash memory, registers, or any other form of writable storage medium known in the art. The memory device 851 may be, but not limited to, a single memory, CD, DVD, ROM, RAM, EEPROM, optical storage, or any other non-volatile storage medium capable of storing digital data.

An optionally incorporated SIM card 849 carries, for instance, important information, such as the cellular phone number, the carrier supplying service, subscription details, and security information. The SIM card 849 serves primarily to identify the mobile station 801 on a radio network. The card 849 also contains a memory for storing a personal telephone number registry, text messages, and user specific mobile station settings.

While the invention has been described in connection with a number of embodiments and implementations, the invention is not so limited but covers various obvious modifications and equivalent arrangements, which fall within the purview of the appended claims. Although features of the invention are expressed in certain combinations among the claims, it is contemplated that these features can be arranged in any combination and order.

Claims

1. A computer-readable storage medium carrying one or more sequences of one or more instructions which, when executed by one or more processors, cause the one or more processors to at least perform the following: allocating radio resources to a user equipment; generating a revoke command to revoke the allocation; initiating transmission of the revoke command to the user equipment; and determining acknowledgement of the revoke command.

2. A computer-readable storage medium according to claim 1, wherein the acknowledgement is signaled using a layer 1 (Ll) protocol, a medium access control (MAC) protocol, or a physical uplink control channel (PUCCH).

3. A computer-readable storage medium according to any one of claims 1 and 2, wherein the revoke command is for an uplink resource, and the acknowledgement is signaled using the revoked uplink resource.

4. A computer-readable storage medium according to claim 3, wherein the acknowledgement includes a pseudo noise sequence to identify the user equipment.

5. A computer-readable storage medium according to any one of claims 1 and 2, wherein the revoke command is transmitted on a physical downlink control channel (PDCCH), and the corresponding acknowledgement is signaled using a physical uplink control channel (PUCCH) resource derived from the PDCCH resource on which the revoke command was transmitted.

6. A computer readable storage medium according to any one of claims 1-5, wherein the resources include physical resource blocks, and the communication link is either an uplink or a downlink.

7. An apparatus comprising a processor and a memory storing executable instructions that if executed cause the apparatus to at least perform the following: allocating radio resources to a user equipment; generating a revoke command to revoke the allocation; initiating transmission of the revoke command to the user equipment; and determining acknowledgement of the revoke command.

8. An apparatus according to claim 7, wherein the acknowledgement is signaled using a layer 1 (Ll) protocol, a medium access control (MAC) protocol, or a physical uplink control channel (PUCCH).

9. An apparatus according to any one of claims 7 and 8, wherein the revoke command is for an uplink resource, and the acknowledgement is signaled using the revoked uplink resource.

10. An apparatus according to claim 9, wherein the acknowledgement includes a pseudo noise sequence to identify the user equipment.

11. An apparatus according to any one of claims 7 and 8, wherein the revoke command is transmitted on a physical downlink control channel (PDCCH), and the corresponding acknowledgement is signaled using a physical uplink control channel (PUCCH) resource derived from the PDCCH resource on which the revoke command was transmitted.

12. An apparatus according to any of claims 7-11, wherein the resources include physical resource blocks, and the communication link is either an uplink or a downlink.

13. A method comprising: allocating radio resources to a user equipment; generating a revoke command to revoke the allocation based on the determination; initiating transmission of the revoke command to the user equipment; and determining acknowledgement of the revoke command.

14. A method according to claim 13, wherein the acknowledgement is signaled using a layer 1 (Ll) protocol, a medium access control (MAC) protocol, or a physical uplink control channel (PUCCH).

15. A method according to any one of claims 13 and 14, wherein the revoke command is for an uplink resource, and the acknowledgement is signaled using the revoked uplink resource.

16. A method according to any one of claims 13 and 14, wherein the revoke command is transmitted on a physical downlink control channel (PDCCH), and the corresponding acknowledgement is signaled using a physical uplink control channel (PUCCH) resource derived from the PDCCH resource on which the revoke command was transmitted.

17. A computer-readable storage medium carrying one or more sequences of one or more instructions which, when executed by one or more processors, cause the one or more processors to at least perform the following steps: receiving a revoke command to revoke an allocation of radio resources; generating an acknowledgement of the revoke command; and initiating transmission of the acknowledgement to a base station.

18. A computer-readable storage medium according to claim 17, wherein the acknowledgement is signaled using a layer 1 (Ll) protocol, a medium access control (MAC) protocol, or a physical uplink control channel (PUCCH).

19. A computer-readable storage medium according to any one of claims 17 and 18, wherein the revoke command is for an uplink resource, and the acknowledgement is signaled using the revoked uplink resource.

20. A computer-readable storage medium according to any one of claims 17 and 18, wherein the revoke command is received on a physical downlink control channel (PDCCH), and the corresponding acknowledgement is signaled using a physical uplink control channel (PUCCH) resource derived from the PDCCH resource on which the revoke command was received.

21. A computer-readable storage medium according to claim 19, wherein the acknowledgement includes a pseudo noise sequence to identify the user equipment.

22. An apparatus comprising a processor and a memory storing executable instructions that if executed cause the apparatus to at least perform the following: receiving a revoke command to revoke an allocation of radio resources; and generating an acknowledgement of the revoke command; and initiating transmission of the acknowledgement to a base station.

23. An apparatus according to claim 23, wherein the acknowledgement is signaled using a layer 1 (Ll) protocol, a medium access control (MAC) protocol, or a physical uplink control channel (PUCCH).

24. An apparatus according to any one of claims 22 and 23, wherein the revoke command is for an uplink resource, and the acknowledgement is signaled using the revoked uplink resource.

25. An apparatus according to any one of claims 22 and 23, wherein the revoke command is received on a physical downlink control channel (PDCCH), and the corresponding acknowledgement is signaled using a physical uplink control channel (PUCCH) resource derived from the PDCCH resource on which the revoke command was received.

26. A computer-readable storage medium according to claim 24, wherein the acknowledgement includes a pseudo noise sequence to identify the user equipment.

27. A method comprising: receiving a revoke command to revoke an allocation of radio resources; generating an acknowledgement of the revoke command; and initiating transmission of the acknowledgement to a base station.

28. A method according to claim 27, wherein the acknowledgement is signaled using a layer 1 (Ll) protocol, a medium access control (MAC) protocol, or a physical uplink control channel (PUCCH).

29. A method according to any one of claims 27 and 28, wherein the revoke command is for an uplink resource, and the acknowledgement is signaled using the revoked uplink resource.

30. A method according to any one of claims 27 and 28, wherein the revoke command is received on a physical downlink control channel (PDCCH), and the corresponding acknowledgement is signaled using a physical uplink control channel (PUCCH) resource derived from the PDCCH resource on which the revoke command was received.